In an information recording medium of a recording type, such as a CD-R (Compact Disc-Recordable), a DVD-R, a DVD-RW, and a DVD+R, for example, as described in patent documents 1 and 2, etc., there is also developed an information recording medium, such as an optical disc, of a multilayer type or dual layer type or multiple layer type, in which a plurality of recording layers are laminated or stacked on the same substrate. Then, on an information recording apparatus, such as a DVD recorder, which performs recording with respect to the dual layer type, i.e., two-layer type optical disc, information is recorded in an irreversible change recording method by heat or the like, or in a rewritable method, into a recording layer located on the front (i.e. on the closer side to an optical pickup) viewed from a laser light irradiation side (hereinafter referred to as an “L0 layer”, as occasion demands), by focusing the laser light for recording on the L0 layer. On the other hand, information is recorded in the irreversible change recording method by heat or the like, or in the rewritable method, into a recording layer located on the rear (i.e. on the farther side to the optical pickup) viewed from the laser light irradiation side (hereinafter referred to as an “L1 layer”, as occasion demands), by focusing the laser light for recording on the L1 layer through the L0 layer.
When information is recorded into the L1 layer, which constitutes such a two-layer type optical disc, the optimum recording power of the laser light with which the L1 layer is irradiated through the recorded L0 layer, as shown in FIG. 22(a), is 44.5 (mW: milliwatt) at which a jitter value is minimal on a parabolic curve in a thin line (with white triangles) in FIG. 22(c), for example. On the other hand, the optimum recording power of the laser light with which the L1 layer is irradiated through the unrecorded L0 layer which has a different light transmittance from that of the recorded L0 layer, as shown in FIG. 22(b), is 46 (mW: milliwatt) at which a jitter value is minimal on a parabolic curve in a thick line (with black triangles) in FIG. 22(c), for example. Thus, there is a need to consider whether or not the L0 layer is recorded, in the case of the recording in the L1 layer. With respect to this, there is devised or invented a recording method in which a so-called recording order is satisfied, wherein the recording order is that the laser light for recording, transmitted through the recorded L0 layer, is to be irradiated, for example. On the other hand, with the L0 layer in an unrecorded state, information is recorded into the L1 layer, by the laser light holding an optimum recording power corresponding to the unrecorded L0 layer. Alternatively, it is judged whether or not an area in the L0 layer facing or opposed to an area scheduled to record therein information is recorded, on the basis of management information, such as a space bit map (SBM), for example. Then, on the basis of the judgment, the information is recorded into the L1 layer. The expression “facing or opposed to” in the present invention may mean that one portion of the first recording layer and one portion of the second recording layer correspond to and face each other, i.e. a position relationship in which they are in substantially the same radial position. Moreover, it may mean a position relationship after consideration of errors, such as an eccentricity.
Patent document 1: Japanese Patent Application Laid Open NO. 2000-311346
Patent document 2: Japanese Patent Application Laid Open NO. 2001-23237